Ledenvergadering 20 Januari 2026 20.00 uur

LET OP HET IS NIET IN SPAUBEEK MAAR IN HET WEVERKE TE SCHIMMERT

Hierbij nodig ik namens het bestuur alle leden van de afdeling uit voor het bijwonen van de Algemene Ledenvergadering (ALV) die zal worden gehouden op dinsdag 20 januari 2026 om 20:00 uur in Het Weverke, Hoofdstraat 77, 6333 BG, Schimmert.

Aftredend bestuur en eventuele opheffing van de afdeling

Vorig jaar januari is de afdeling “gered”. Er waren geen kandidaten voor een bestuursfunctie, maar tijdens de vergadering bleken uiteindelijk drie leden bereid om een bestuur te vormen. Voor alle drie gold – samengevat – dat zij hun taak als voorwaardelijk zagen en wilden zien hoe het zou gaan verlopen.

Het bestuur heeft het afgelopen jaar geëvalueerd en is tot de conclusie gekomen dat het gebrek aan belangstelling voor activiteiten niet is veranderd, nog daargelaten de bereidheid van leden om activiteiten te organiseren of daarbij mee te helpen. De wekelijkse bijeenkomsten worden weliswaar bezocht, maar in de praktijk komt het erop neer dat het niet uitmaakt of er een bestuur is of niet.

Daarom hebben Guido, PA4GR, Mark, PC9DB en Henk, PA2S besloten af te treden en zich niet herkiesbaar te stellen.

Wanneer zich geen opvolgers melden, zal het huidige bestuur besluiten om de afdeling op te heffen. Als er geen voortzetting mogelijk is, zal in een aparte vergadering eind februari of begin maart het definitieve besluit daartoe moeten worden genomen. Daarbij zal onder andere ook beslist worden over de bestemming van het batig saldo.

Een en ander leidt tot de volgende agenda:

1. Opening door de voorzitter met terugblik 2025

2. Verslag van de penningmeester

3. Verslag van de kascontrolecommissie

4. Aftreden en eventueel verkiezen nieuw bestuur

5. Afhankelijk van punt 4 besluit over vervolgstappen.

Deelnemers moeten een geldig lidmaatschap hebben en de presentielijst tekenen.

Wij streven ernaar om uiterlijk het komende weekeinde vergaderstukken toe te zenden.

Wij rekenen op uw komst!

The Cutting Truth About Variable Capacitors

If you’ve seen a big air-variable capacitor, you may have noticed that some of the plates may have slots cut into them. Why? [Mr Carlson] has the answer in the video below. The short answer: you can bend the tabs formed by the slots to increase or decrease the capacitance by tiny amounts for the purpose of tuning.

For example, if you have a radio receiver with a dial, you can adjust the capacitor to make certain spots on the dial have an exact frequency. Obviously, you can only adjust in bands depending on how many slots are in the capacitor. Sometimes the adjustments aren’t setting the oscillator’s frequency. For example, the Delco radio he shows uses the capacitor to peak the tuning at the specified frequency.

You usually only find the slots on the end plates and, as you can see in the video, not all capacitors have the slots. Of course, bending the plates with or without slots will make things change. Just don’t bend enough to short to an adjacent plate or the fixed plates when the capacitor meshes.

Of course, not all variable capacitors have this same design. We’ve seen a lot of strange set ups.

 

Afdelingsbijeenkomsten in de feestmaand

Via deze weg willen wij graag onder de aandacht brengen dat op dinsdag 9 december de laatste afdelingsbijeenkomst van 2025 gehouden zal worden.

Vanaf dinsdag 6 januari 2026 zullen de afdelingsbijeenkomsten weer hervatten, zoals gebruikelijk vanaf 20:00 bij Eetcafé Spech in Spaubeek.

An Introduction To Analog Filtering

One of the major difficulties in studying electricity, especially when compared to many other physical phenomena, is that it cannot be observed directly by human senses. We can manipulate it to perform various tasks and see its effects indirectly, like the ionized channels formed during lightning strikes or the resistive heating of objects, but its underlying behavior is largely hidden from view. Even mathematical descriptions can quickly become complex and counter-intuitive, obscured behind layers of math and theory. Still, [lcamtuf] has made some strides in demystifying aspects of electricity in this introduction to analog filters.

The discussion on analog filters looks at a few straightforward examples first. Starting with an resistor-capacitor (RC) filter, [lcamtuf] explains it by breaking its behavior down into steps of how the circuit behaves over time. Starting with a DC source and no load, and then removing the resistor to show just the behavior of a capacitor, shows the basics of this circuit from various perspectives. From there it moves into how it behaves when exposed to a sine wave instead of a DC source, which is key to understanding its behavior in arbitrary analog environments such as those involved in audio applications.

There’s some math underlying all of these explanations, of course, but it’s not overwhelming like a third-year electrical engineering course might be. For anyone looking to get into signal processing or even just building a really nice set of speakers for their home theater, this is an excellent primer. We’ve seen some other demonstrations of filtering data as well, like this one which demonstrates basic filtering using a microcontroller.

Retro Style VFO Has Single-Digit Parts Count

Not every project has to be complicated– reinventing the wheel has its place, but sometimes you find a module or two that does exactly what you want, and the project is more than halfway done. That the kind of project [mircemk]’s Simple Retro Style VFO is — it’s a variable frequency oscillator for HAM and other use, built with just a couple of modules.

Strictly speaking, this is all you need for the project.

The modules in question are the SI5351 Clock Generator module, which is a handy bit of kit with its own crystal reference and PLL to generate frequencies up to 150 MHz, and the Elecrow CrowPanel 1.28inch-HMI ESP32 Rotary Display. The ESP32 in the CrowPanel controls the SI5351 module via I2C; control is via the rest of the CrowPanel module. This Rotary Display is a circular touchscreen surrounded by a rotary display, so [mircmk] has all the inputs he needs to control the VFO.

To round out the parts count, he adds an appropriate connector, plus a power switch, red LED and a lithium battery. One could include a battery charger module as well, but [mircmk] didn’t have one on hand. Even if he had, that still keeps the parts count well inside the single digits. If you like video, we’ve embedded his about the project below; if not the write up on Hackaday.io is upto [mircmk]’s typical standard. 

People have been using the SI5351 to make VFOs for years now, but the addition of the round display makes for a delightfully retro presentation.

Thanks to [mircmk] for the tip.

 

All Handheld Antennas Are Not Born The Same

If you own a handheld transceiver of any type then the chances are it will come with a “rubber duck” style antenna. These flexible rubber-coated antennas are a compromise in performance, being significantly smaller than a wavelength at their frequency of operation. [OM40ET] has an interesting video in which he investigates this by tearing down a cheap rubber duck antenna and an even cheaper fake.

These antennas usually have a flexible upper section and a bulge at the bottom over the connector. The fake one has nothing in the bulge except the antenna wire and thus has a very high SWR, while the “real” one has a loading coil. This coil is an interesting design, because it’s designed such that the antenna has two resonant points at the 2 metre and 70 centimetre amateur bands. On paper it’s a tapped coil fed at the tap through a capacitor for matching, but a more detailed appraisal will tell you that the two halves of the coil are designed to return those two resonances. It’s still a not-very-good antenna, but the fact that it works at all is something.

If you want something better at VHF and haven’t got much space, all is not lost. We recently featured a VHF magnetic loop.

 

Cheap VHF Antenna? Can Do!

The magnetic loop antenna is a familiar sight in radio amateur circles as a means to pack a high performance HF antenna into a small space. It takes the form of a large single-turn coil made into a tuned circuit with a variable capacitor, and it provides the benefits of good directionality and narrow bandwidth at the cost of some scary RF voltages and the need for constant retuning. As [VK3YE] shows us though, magnetic loops are not limited to HF — he’s made a compact VHF magnetic loop using a tin can.

It’s a pretty simple design; a section from the can it cut out and made into a C shape, with a small variable capacitor at the gap. The feed comes in at the bottom, with the feed point about 20 % of the way round the loop for matching. The bandwidth is about 100 MHz starting from the bottom of the FM broadcast band, and he shows us it receiving broadcast, Airband, and 2 meter signals. It can be used for transmitting too and we see it on 2 meter WSPR, but we would have to wonder whether the voltages induced by higher power levels might be a little much for that small capacitor.

He’s at pains to point out that there are many better VHF antennas as this one has no gain to speak of, but we can see a place for it. It’s tiny, if you’re prepared to fiddle with the tuning its high Q gets rid of interference, and its strong side null means it can also reduce unwanted signals on the same frequency. We rather like it, and we hope you will too after watching the video below.

 

Why Does The FCC Care About Computers?

Unless you are over a certain age, you probably take it for granted that electronic gadgets you buy have some FCC marking on them. But it wasn’t always true. [Ernie] submits that the FCC’s regulation of the computer industry was indirectly the result of the success of CB radio in that same time period.

Today, there is a high chance you don’t watch TV directly over the airwaves or even consume audio from a traditional radio station. Even if you do, the signal is increasingly likely to be digital. But only analog radio and TV were highly susceptible to interference. When a professional radio station or the power company interfered with you watching I Love Lucy, you could count on them to resolve it. Even ham radio operators, a small segment of the population, would, in general, graciously help you if their transmissions interfered with your equipment.

Never mind that, in many cases, it was the cheap TV or some other problem on the receiving end. Then there was another source of potential interference: CB radio. At first, you were about as likely to encounter a CB operator as a ham radio operator. But then in the 1970s, CB exploded, becoming a cultural phenomenon, and you can hear what a state it was in by watching the contemporary TV report in the video below.

 

This explosion of operators who did nothing more than apply for a license (if they even bothered to do so) and bought their equipment at a local store had no idea how to help curb interference, even if they wanted to. In 1977, the AP reported that 83% of the FCC’s TV interference complaints involved CB radio.

Early computers were also very noisy on the radio bands. So much so that early attempts at computer audio output were simply modulating the radio frequency interference. Again, at first, this wasn’t a huge problem. But as computers became more common, so did computer-related interference, and the FCC didn’t want to deal with another CB radio-style explosion.

The rest is, as they say, history, and [Ernie] covers it all in the post. Getting a product approved by the FCC isn’t trivial, but if you have to do it, we have some advice.